In Situ Transformation of Metal Molybdates into Polymetallic Sulfides with Enriched Edge Sites for High-Performance Supercapacitors

Amorphous/polycrystalline NiMn selenide for high-performance supercapacitors

Transition-metal selenides have been extensively studied as promising electrode materials for supercapacitors. Engineering amorphous/crystalline heterostructures is an effective strategy to improve rich active sites for accelerating redox reaction kinetics but still lacks exploration. In this study, an amorphous/crystalline heterostructure was designed and constructed by selenizing the self-sacrificial template NiMnS to generate amorphous Mn/polycrystalline Ni0.85Se-NiSe2 heterophase via the phase transformation from metal sulfide into metal selenide. The synergy of the complementary multi-components and amorphous/polycrystalline heterophase could enrich electron/ion-transport channels and expose abundant active sites, which accelerated electron/ion transfer and Faradaic reaction kinetics during charging/discharging. As expected, the optimal NiMnSe exhibited a high specific charge (1389.1 C g-1 at 1 A g-1), a good rate capability, and an excellent lifespan (88.9% retention). Moreover, the fabricated NiMnSe//activated carbon device achieved a long cycle life and energy density of 48.0 W h kg-1 at 800 W kg-1, shedding light on the potential for use in practical applications, such as electrochemical energy-storage devices.

High-efficiency activated phosphorus-doped Ni2S3/Co3S4/ZnS nanowire/nanosheet arrays for energy storage of supercapacitors

Transition metal sulfides (TMS) have been considered as a promising group of electrode materials for supercapacitors as a result of their strong redox activity, but high volumetric strain of the materials during electrochemical reactions causes rapid structural collapse and severe capacity loss. Herein, we have synthesized phosphorus-doped (P-doped) Ni2S3/Co3S4/ZnS battery-type nanowire/nanosheet arrays as an advanced cathode for supercapacitor through a two-step process of hydrothermal and annealing treatments. The material has a one-dimensional nanowire/two-dimensional nanosheet-like coexisting microscopic morphology, which facilitates the exposure of abundant active centers and promotes the transport and migration of ions in the electrolyte, while the doping of P significantly enhances the conductivity of the electrode material. Simultaneously, the element phosphorus with similar atomic radii and electronegativity to sulfur may act as electron donors to regulate the electron distribution, thus providing more effective electrochemically active sites. In gratitude to the synergistic effect of microstructure optimization and electronic structure regulation induced by the doing of P, the P-Ni2S3/Co3S4/ZnS nanoarrays provide a superior capacity of 2716 F g-1 at 1 A/g, while the assembled P-Ni2S3/Co3S4/ZnS//AC asymmetric supercapacitor exhibits a high energy density of 48.2 Wh kg-1 at a power density of 800 W kg-1 with the capacity retention of 89 % after 9000 cycles. This work reveals a possible method for developing high-performance transition metal sulfide-based battery-like electrode materials for supercapacitors through microstructure optimization and electronic structure regulation.